Passive Monitor Controller Distortion

[CiaoPatsy]

Hey guys, just built a passive monitor controller based on the Pro Harmonic plans. It's working well except for some distortion im getting when I'm playing mastered (very loud) audio. I have the 10k alps pot w 4.7k resistors exactly how it is in the Pro Harmonic plans.  http://www.proharmonic.com/articles/AT78_OTB.pdf

Would it help to put higher value resistors in place of the 4.7k? If so what would be a logical value to use?

Or do I need to pad down the input into the controller?

Thanks!

 

[ruffrecords]

Hey guys, just built a passive monitor controller based on the Pro Harmonic plans. It's working well except for some distortion im getting when I'm playing mastered (very loud) audio.

There is no reason a passive monitor controller should introduce distortion unless it is too heavy a load for the source. What are you driving it from?

Cheers

Ian

 

[CiaoPatsy]

That's what I thought as well.

Going from the analog outs of my Lynx Aurora into it. The distortion amount in the signal  stays the same no matter where the volume pot is turned.

 

[ruffrecords]

I just checked the Aurora spec and it says its output R is 100 ohms and it will drive a 600 ohm load. You are loading is with not less than 10K so it should be fine. This is really odd. Have you tried it with some lower level material? Have you actually measured the distortion?

Cheers

Ian

 

[CiaoPatsy]

Thanks for trying to help.

Using it on normal tracking and mixing sessions it's fine.

I've tried switching the operating level of pro tools to the monitor outs and it does take away the distortion.

I had a dangerous d box as my controller before and they perform the same until I play mastered audio through this new one.

 

[ruffrecords]

Can you post a sample of the distorted sound. It might give a clue as to what is causing it.

Check the values of the two 4K7 resistors. occasionally you miss marked ones

Cheers

Ian

 

[Monte McGuire]

Here's a silly idea - maybe the output of the Aurora with 'mastered' signals is the problem? In other words, have you ever heard this 'mastered' signal sound good through any other means? In other words, your passive monitor solution is properly conveying the distorted signal that the Aurora is producing (which might be a problem with the signal fed to the Aurora?)

This is exactly what you want a monitor controller to do - to tell you when your signal stinks, and maybe your monitor controller is working properly? Dig in a bit and see where the blame can be placed...

 

[CiaoPatsy]

I built this controller because I got rid of my dangerous d box. They perform  identically to my ears until I run mastered tracks. I get the distortion on this controller and not on the dbox. It could be that the aurora is distorting and that's pretty much what I've concluded. Thinking more about it, I remembered that I had the dbox set up using its D/A which might explain why I wasn't getting as much distortion vs the lynx.

 

[ruffrecords]

I built this controller because I got rid of my dangerous d box. They perform  identically to my ears until I run mastered tracks. I get the distortion on this controller and not on the dbox. It could be that the aurora is distorting and that's pretty much what I've concluded. Thinking more about it, I remembered that I had the dbox set up using its D/A which might explain why I wasn't getting as much distortion vs the lynx.

That explains it. You are not comparing like with like. Can you try feeding the analogue outs of the lynx into dbox?

Do the peak LEDs of the Aurora light up with this mastered material?

Cheers

Ian

 

[CiaoPatsy]

I sold the Dbox so thats a no go. Yes the Aurora does show clipping on the meters when I'm listening to that mastered stuff. The distortion at the controller is really extreme though, which isn't what I ever experienced with the dbox, which is why I was freaking out.

Also, the passive controller definitely seems to like to be fed a quieter level.  Maybe the d box has more attenuation?

 

[ruffrecords]

The lynx manual clearly states "The upper row of red LEDs indicate overload. "

I think it is the lynx that likes lower levels not the passive controller.

Cheers

Ian